Source for thermal physical vapor deposition of organic electroluminescent layers

ABSTRACT

The present invention disclosed the deposition source installed in a chamber, heated by applied electric power to transfer heat to a vapor deposition material received therein and applying a vaporized deposition material generated therein to a substrate to form deposition organic electroluminescent layers onto the substrate, and comprising a vessel consisted of a top plate on which a vapor efflux aperture is formed, a side wall, and a bottom wall; a heating means for supplying heat to the deposition material received in the vessel, the heating means being capable of moving vertically; and a means for moving the heating means (or the bottom wall), the moving means (or the bottom wall) being operated in response to the signal of a sensing means on varied distances between the heating means and the surface of said deposition material. Thus, the heating means is moved downward (or the bottom wall) is moved upward by the moving means to maintain the distance between the heating means (or the substrate to be coated) and the surface of the deposition material at an initially-set value when the thickness of the deposition material is decreased.

This application is a Divisional of Ser. No. 10/621,471 filed on Jul.18, 2003 now U.S. Pat. No. 7,025,832, which claims priority to KoreanApplication Nos. 42271/2002 filed Jul. 19, 2002, 58116/2002 filed Sep.25, 2002 and 59786/2002 filed Oct. 1, 2002 in Korea. The above documentsare incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to a deposition source for thermalphysical vapor deposition of organic electroluminescent layers, andparticularly to a deposition source capable of forming a uniformelectroluminescent layer on the entire surface of a substrate bycompensating increase of the distance between a deposition material anda heating means (or the substrate) from change of the thickness of thedeposition material.

BACKGROUND OF THE INVENTION

Thermal physical vapor deposition process, which is one of the processesfor depositing an organic electroluminescent device, is a technique tocoat an electroluminescent layer on a substrate in a housing withvaporized deposition material. In the deposition process, the depositionmaterial is heated to the point of vaporization and the vapor of thedeposition material is condensed on the substrate to be coated after thedeposition material is moved out of the deposition source. This processis carried out with both deposition source holding the material to bevaporized and substrate to be coated in a vessel with the pressure rangeof 10⁻⁷ to 10⁻² Torr.

Generally speaking, the deposition source to hold the depositionmaterial is made from electrically resistant materials whose temperatureis increased when electrical current is passed through walls (member).When the electrical current is applied to the deposition source, thedeposition material inside is heated by radiation heat from the wallsand conduction heat from contact with the walls. Typically, thedeposition source is in the shape of box with aperture to allow vaporefflux toward the direction of the substrate.

Thermal physical vapor deposition source has been used to vaporize anddeposit onto the substrate layers comprised of a wide range ofmaterials, for example, organics of low temperature, metals, orinorganic compounds of high temperature. In the case of organic layerdeposition, the starting material is generally powder. Organic powderhas been recognized as giving a number of disadvantages for this type ofthermal vaporization coating. First, many organics are relativelycomplex compounds (high molecular weight) with relatively weak bonding,and so intensive care must be taken to avoid decomposition during thevaporization process. Second, the powder form can give rise to particlesof non-vaporized electroluminescent materials. The particles leave thedeposition source with vapor and are deposited as undesirable lumps onthe substrate. Such lumps are also commonly referred to as particulateor particulate inclusion in the layers formed on the substrate.

Further exacerbation is found in that the powder form has a very largesurface area enough to support water sucked in or absorbed or volatileorganics, and the volatile organics can be released during heating andcan cause gas and particulates to be thrown outward from the depositionsource toward the substrate. Similar considerations pertain to materialswhich are melted before vaporization and form droplets erupted to thesubstrate surface.

These unwanted particulates or droplets may result in unacceptabledefects in products, particularly in electronic or optical products,dark spots may appear in images, or shorts or opens may result infailures within electronic devices.

Organic deposition apparatuses have been proposed to heat the organicpowder more uniformly and to prevent the bursts of particulates ordroplets from reaching the substrate. Many designs for complicatedbaffling structures between the source material and the vapor effluxaperture have been suggested to ensure vapor exits.

FIG. 1 is a schematic sectional view showing the inner structure of aconventional apparatus for depositing an organic electroluminescentlayer, and shows a deposition source 10 mounted in a vacuum chamber 13of the deposition apparatus and a substrate 12 located above thedeposition source 10. The substrate 12 to be coated with the organicelectroluminescent layers is mounted to an upper plate 13-1 of thechamber 13, and the deposition source 10 to have a deposition material20 (organic material) is mounted on a thermally insulating structure 14fixed to a bottom wall 13-2 of the chamber 13.

FIG. 2 a is a sectional view showing the inner structure of thedeposition source shown in FIG. 1, and shows that a baffle 11B isprovided in the deposition source 10 to prevent particulates or dropletscontained in the vapor of the deposition material 20 from directlyexiting through a vapor efflux aperture 11C formed on the top plate 11Aof the deposition source 10. The baffle 11B corresponds to the vaporefflux aperture 11C and is fixed to a number of support rods 11B-1 fixedto the top plate 11A of the deposition source 10 to maintain certainspace from the top plate 11A.

The deposition apparatus using the deposition source 10 with the abovestructure has a heater or a heating means on (or under) the top plate11A, or is constructed for the top plate 11A to have a heater in orderto transfer heat to the deposition material 20 located around the centeraway from the side wall 11D. Thus, the heat generated at the side wall11D as well as from the top plate 11A is transferred directly to thedeposition material 20 so that the deposition material 20 is heated andvaporized. The vapor of vaporized deposition material 20 is moved alongthe surface of the baffle 11B and deposited on the substrate 12 (inFIG. 1) after exit through the vapor efflux aperture 11C.

FIG. 2 b is a sectional view showing the change of distance between thetop plate of the deposition source in FIG. 1 and the deposition materialafter the deposition is processed for a certain amount of time. Thus,FIG. 2 b shows a state that the distance between the top plate 11A andthe surface of the deposition material 20 is increased.

As explained above, the quantity of the deposition material 20 receivedin the deposition source 10 is decreased gradually by heating andvaporizing reactions in progressing the deposition process also thethickness of the deposition material 20 is decreased. Thus, in a certainamount of time, the initial distance (A in FIG. 2 a) between the topplate 11A and the surface of the deposition material 20 in thedeposition source is remarkably increased (a in FIG. 2 b).

Due to increase of the distance between the top plate 11A and thesurface of the deposition material 20, the heat transfer path isincreased so that the deposition rate (that is, vaporization rate of thedeposition material) set at the initial stage is decreased. Thus, inorder to maintain the initially-set deposition rate, the temperature ofthe top plate 11A acting as the heater heating the deposition material20 is needed.

In particular, while the deposition process is progressed, the distancebetween the top plate 11A and the surface of the deposition material 20is increased. Under this situation, the sufficient heat generated at thetop plate 11A cannot reach the deposition material 20, and so thedeposition material located on the center is not vaporized though theheat generated from the side wall 11D is supplied. Consequently, if theinput amount of the deposition material 20 is high (that is, thethickness of the deposition material 20 is high), it is difficult toexpect that all the deposition material is vaporized.

Also, the distance between the substrate 12 and the deposition material20, which is directly related to the uniformity of deposition layer, isincreased to result in change of the deposition characteristics in time.

Low molecule organic electroluminescent material contains a large amountof organic material unstable to heat, and causes a problem of loweringthe characteristics of the organic electroluminescent material byinducing resolution or change of the material characteristics due toexcessive radiant heat in the deposition process. In addition,additional processes for cooling the chamber, exhausting the vacuumpressure, and re-vacuumizing are required to supply new depositionmaterial to replenish the exhausted deposition material because thedeposition process is conducted under high vacuum condition. Suchadditional processes cause loss of the process time.

In order to solve these problems, it is desirable to maintain uniformlythe initial deposition characteristics (for example, vaporization rateof the deposition material) in supplying more deposition material in thedeposition source at a time.

On the other hand, in the deposition source 10 with the structure shownin FIG. 2 a and FIG. 2 b, the side wall 11D acts as a heating unit (forexample, structure which coils are wound around the side wall 11D). Asshown in FIG. 1, however, since the sidewall 11D is exposed to theexterior, the thermal efficiency is lowered because all heat generatedat the side wall 11D is not transferred to the deposition material 20and some heat is radiated to the exterior.

In addition, as describe above, in progressing the deposition process,the deposition material 20 supplied in the deposition source 10 isconsumed, and so the thickness of the deposition material 20 isdecreased. Thus, heat is generated at the sidewall 11D corresponding tothe portions without the deposition material and is not transferreddirectly to the deposition material, which contributes to energy waste.

Another drawback of the deposition source 10 is that the heat generatedat the top plate 11A and the side wall 11D is not sufficientlytransferred to the deposition material 20 located at the lower portionof the deposition source 10, that is, the deposition material 20adjoining the surface of the bottom wall 11E. As a result, all of thedeposition material 20 is not heated and vaporized. Particularly,depending on positions within the deposition source 10, the temperatureof each deposition material 20 becomes different, that is, thermalgradient within the deposition source. Therefore, it is difficult toform a uniform deposition layer on the substrate.

SUMMARY OF THE INVENTION

An object of the present invention is to provide the deposition sourcewhich can compensate change of the distance between the heating meansand the surface of the deposition material caused by decrease of thethickness of the deposition material according to consumption of thedeposition material in the deposition process for the purpose of solvingproblems caused by increase of the distance between the top plate(heating means) of the deposition source and the surface of thedeposition material supplied into the deposition source from thedeposition process.

Another object of the present invention is to provide the depositionsource which can enhance thermal efficiency through preventing heatgenerated at the heating means from exiting to the exterior by adding aheat-cutting function.

Further, another object of the present invention is to provide thedeposition source for forming organic electroluminescent layers whichcan obtain a uniform deposition layer by minimizing factors oftemperature change and by efficiently using all the deposition materialthrough supplying heat to the deposition source adjoining the surface ofthe bottom wall.

The deposition source according to the present invention is installed ina chamber, heated by applied electric power to transfer heat to a vapordeposition material received therein and applying a vaporized depositionmaterial generated therein to a substrate to form deposition organicelectroluminescent layers onto the substrate, and comprises a vesselconsisted of a top plate on which a vapor efflux aperture is formed, aside wall, and a bottom wall; a heating means for supplying heat to thedeposition material received in the vessel, the heating means beingcapable of moving vertically; and a means for moving said heating means,the moving means being operated in response to the signal of a sensingmeans on varied distances between the heating means and the surface ofsaid deposition material. Thus, the heating means is moved downward bythe moving means to maintain the distance between the heating means andthe surface of the deposition material at an initially-set value whenthe thickness of the deposition material is decreased.

Another deposition source according to the present invention isinstalled in a chamber, to form deposition organic electroluminescentlayers onto the substrate, by applying a vaporized deposition materialgenerated therein to a substrate, by transferring heat to a vapordeposition material received therein, heated by applied electric power,and comprises a vessel consisted of a top plate on which a vapor effluxaperture is formed, a side wall, and a bottom plate, the bottom platebeing capable of moving vertically; a heating means for supplying heatto the deposition material received in the vessel; and a means formoving said bottom plate, the moving means being operated in response tothe signal of a sensing means on varied distances between the heatingmeans and the surface of the deposition material. Thus, the bottom plateis moved upward by the moving means to maintain the distance between theheating means and the surface of the deposition material and thedistance between the substrate to be coated and the surface of thedeposition material at an initially-set value when the thickness of thedeposition material is decreased.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more clearly understood from the detaileddescription in conjunction with the following drawings.

FIG. 1 is a schematic sectional view of a conventional apparatus fordepositing an organic electroluminescent layer.

FIG. 2 a is a sectional view showing the structure of the depositionsource shown in FIG. 1 prior to performing the deposition process;

FIG. 2 b is a sectional view showing change of the distance between thetop plate of the deposition source and the deposition material in FIG. 1after the deposition process is performed for a certain period of time.

FIG. 3 a is a sectional view of the deposition source according to thefirst embodiment of the present invention.

FIG. 3 b is a detailed view of part 3 b in FIG. 3 a.

FIG. 3 c is a view showing relationship between the top plate of thedeposition source and the deposition material after the depositionprocess is completed.

FIG. 4 is a sectional view of the deposition source according to thesecond embodiment of the present invention.

FIG. 5 is a sectional view of the deposition source according to thethird embodiment of the present invention.

FIG. 6 is a sectional view taken along line 6-6 in FIG. 5.

FIG. 7 is a schematic perspective view showing relationship between thesubstrate and the deposition source according to the fourth embodiment.

FIG. 8 a is a plane view of the substrate showing the initial statewhich the electroluminescent layer is deposited on the surface using thedeposition source shown in FIG. 7.

FIG. 8 b is a plane view of the substrate showing the state thatdeposition of the electroluminescent layer has been completed under thestate that the deposition source (or substrate) shown in FIG. 7 has beenmoved.

FIG. 9 a and FIG. 9 b are schematic sectional views showing variousshapes of the deposition source according to the fourth embodiment ofthe present invention.

DETAILED DESCRIPTON OF THE INVENTION

Reference should be made to the drawings. The same reference numeralsare used throughout the drawings to designate same or similar elements.

First Embodiment

FIG. 3 a is a sectional view of the deposition source according to thefirst embodiment of the present invention. A deposition source 100according to the first embodiment is a vessel consisted of a top plate101, a side wall 102, and a bottom wall 103. The deposition source 100contains solid organic electroluminescent vapor deposition material 20(hereinafter, referred to as “deposition material”). A vapor effluxaperture 101A is formed on the top plate 101. The function of the vaporefflux aperture 101A is to discharge vapor of vaporized depositionmaterial from the deposition source 100. A baffle member 104 fixed to alower surface of the top plate 101 corresponds to the efflux aperture101A.

The top plate 101 can act as a heating means (heater) for supplying heatto the deposition material 20 or a separate heating means can be placedon (or below) the top plate 101. In the description below, a case wherethe top plate 101 acts as a heating means will be explained as anexample.

The most important feature of the first embodiment as shown in FIG. 3 ais that the top plate 101 of the deposition source 100 can be verticallymoved. A movement means 151 to move the top plate 101 is mounted to thetop plate 101.

The movement means 151 used in the deposition source 100 according tothe first embodiment is a hydraulic or pneumatic cylinder. Two supportbrackets 154 fixed a the side wall of the chamber (13 in FIG. 1) areextended above the deposition source 100, and the cylinders 151 aremounted to each end portion of the brackets 154. Rods 152 of eachcylinder 151 are fixed to both sides of the top plates 101, andtherefore, each cylinder 151 does not have any effect on vapor efflux ofthe deposition material 20 through the aperture 101A of the top plate101.

On the other hand, each cylinder 151 is controlled by a control meanswhich is not shown in FIG. 3 a, and the control means is connected to asensing means 153 (for example, optical sensor) installed on the lowersurface of the baffle 104 so that the control means can control eachcylinder 151 according to a signal from the sensing means 153.

FIG. 3 b is a detailed view showing part 3 b in FIG. 3 a. FIG. 3 b showspartially the structure of the side wall 102 and the top plate 101 whichcan be vertically moved along the side wall 102 of the deposition source100.

A number of vertical grooves 102-1 are formed on the inner surface ofthe side wall 102, and protrusions 101-1 are formed on the outercircumference surface of the top plate 101. Each protrusion 101-1corresponds to each groove 102-1 and can be received in thecorresponding groove 102-1 when the top plate 101 and the side wall 102are assembled. Thus, when the top plate 101 is moved vertically, eachprotrusion 101-1 is moved along the corresponding groove 102-1.Consequently, the top plate 101 can be moved smoothly in the verticaldirection without any deviation to the side wall 102 from the initiallocation.

FIG. 3 c is a view showing relationship between the top plate of thedeposition source and the deposition material after the depositionprocess is completed. The function of the deposition source constructedas described above will be explained in reference to FIG. 3 a and FIG. 3c.

As explained above, in the depositing process, the quantity of thedeposition material 20 received in the deposition source 100 isdecreased gradually by the heating and vaporizing action. Thus, thedistance between the surface of the deposition material 20 and the topplate 101 is changed (increased). The sensing means 153 mounted on thelower surface of the baffle 104 senses this change of the distancebetween the surface of the deposition material 20 and the top plate 101,and then transmits the sensed signal to the control means.

The control means calculates the distance between the surface of thedeposition material 20 and the top plate 101 (that is, sum of thedistance between the surface of the deposition material 20 and thesensing means 153, and the distance between the lower surface of thebaffle 104 and the top plate 101) on the basis of the signalstransmitted from the sensing means 153, and then compares the calculateddistance with the initially-set distance (value).

As a result of the above comparison, if the distance between the surfaceof the deposition material 20 and the top plate 101 is changed, thecontrol means operates each cylinder 151. By operating each cylinder151, the rods 152 of each cylinder 151 are extended downward so that thetop plate 101 fixed to the ends of the rods 152 is moved downward alongthe side wall 102.

If the distance between the surface of the deposition material 20 andthe top plate 101 becomes the same as the initially-set distance (A inFIG. 3 a) by downward movement of the top plate 101, that is, when thedistance between the surface of the deposition material 20 and the topplate 101 calculated by the control means on the basis of the signalstransmitted from the sensing means 153 becomes the same as theinitially-set distance, the control means halts the operation of eachcylinder 151.

The downward movement of the top plate 101 caused by the control meansand each cylinder 151 is continued during the deposition process. Aftervaporizing all of the deposition material 20, the control means makesthe rods 152 of each cylinder 151 return to the initial state as shownin FIG. 3 a. Then, the top plate 101 of the deposition source 100returns to its initial position, and thereafter, new deposition materialis supplied to the deposition source 100.

On the other hand, FIG. 3 a and FIG. 3 c show that the optical sensor153 acting as the sensing means is installed on the lower surface of thebaffle 104, but the optical sensor 153 can be installed at any positionincluding the lower surface of the top plate 101 as long as the opticalsensor 153 does not hinder the deposition process and can sense thedistance between the surface of the deposition material 20 and the topplate 101.

Second Embodiment

FIG. 4 is a sectional view of the deposition source according to thesecond embodiment of the present invention. The entire structure of adeposition source 200 according to this embodiment is the same as thatof the deposition source 100 shown in FIG. 3 a and FIG. 3 c. In thisembodiment, a top plate 201 can act as a heating means (heater) forsupplying heat to the deposition material 20 or a separate heating meanscan be placed on (or below) the top plate 201. In the description below,a case where the top plate 201 acts as a heating means will be explainedas an example.

The most important feature of the deposition source 200 according to thesecond embodiment is that a bottom plate 203 can be moved vertically inresponse to change of the distance between the surface of the depositionmaterial 20 and the top plate 201.

As described above, the uniformity of the deposition layer to be formedon the surface of the substrate (12 in FIG. 1) depends on change of thedistance between the substrate 12 and the deposition material 20. In thedeposition source 100 shown in FIG. 3 a, change of the distance betweenthe top plate 101 and the deposition material 20 can be compensated bythe vertical movement of the top plate 101, but a means to adjust changeof the distance between the substrate 12 and the deposition material 20is not disclosed.

In order to compensate change of the distance between the substrate 12and the deposition material 20, the deposition source 200 according tothis embodiment has the stricture which the bottom plate 203 can bemoved vertically along a side wall 202.

A movement means 251 for moving the bottom plate 203 is mounted underthe bottom plate 203 on which the deposition material 20 is located. Themovement means used in the deposition source 200 according to the secondembodiment is a hydraulic or pneumatic cylinder. The cylinder 251 isinstalled on a bottom wall 13-2 of the chamber 13 shown in FIG. 1, a rod252 of the cylinder 251 is passed through the bottom wall 13-2, and theend of the rod 252 is fixed to the lower surface of the bottom plate203. However, the structure shown in FIG. 4 is merely an example, and sothe cylinder having another structure can be installed.

In the this embodiment, the cylinder 251 is controlled by a controlmeans which is not shown in FIG. 4, the control means is connected to asensing means 253 (for example, optical sensor) so that the controlmeans controls the cylinder 251 according to the signal transmitted fromthe sensing means 253.

On the other hand, a number of vertical grooves are formed on the innersurface of the side wall 202, and a number of protrusions are formed onthe outer circumference surface of the bottom plate 203. Each protrusioncorresponds to each groove and can be received in the correspondinggroove. Therefore, the bottom plate 203 can be moved smoothly in thevertical direction without any deviation to the side wall 202 from theinitial location. This structure of the second embodiment is the same asthat of the first embodiment as shown in FIG. 3 c except difference ofthe member on which the protrusions are formed. Therefore, a furtherdetailed description on the protrusions and grooves is omitted.

In the depositing process, the quantity of the deposition material 20received in the deposition source 200 is decreased gradually by theheating and vaporizing actions. Thus, the distance between the substrate(12 in FIG. 1) and the deposition material 20 is increased (surely, thedistance between the surface of the deposition material 20 and the topplate 201 is also increased, and the increased distance between thesurface of the deposition material 20 and the top plate 201 is the sameas the increased distance between the substrate 12 and the surface ofthe deposition material 20).

The sensing means 253 mounted to a lower surface of a baffle 204 senseschange of the distance between the surface of the deposition material 20and the top plate 201, and then transmits the sensed signal to thecontrol means. The control means calculates the distance between thesurface of the deposition material 20 and the top plate 201 on the basisof the signals transmitted from the sensing means 253, and then comparesthe calculated distance with the initially-set distance.

As a result of the above comparison, if the distance between the surfaceof the deposition material 20 and the top plate 201 is changed, thecontrol means operates the cylinder 251 installed under the bottom plate203. By operating of the cylinder 251, the rod 252 of the cylinder 251is extended upward so that the bottom plate 203 fixed to the end of therod 252 is moved upward along the side wall 202.

If the distance between the surface of the deposition material 20 andthe top plate 201 becomes the same as the initially-set distance (A inFIG. 3 a) by the upward movement of the bottom plate 203, that is, whenthe distance between the surface of the deposition material 20 and thetop plate 201 calculated by the control means on the basis of thesignals transmitted from the sensing means 253 becomes the same as theinitially-set distance, the control means halts the operation of thecylinder 251.

The upward movement of the bottom plate 203 caused by the control meansand the cylinder 251 is continued during the deposition process. Aftervaporizing all of the deposition material 20, the control means makesthe rod 252 of the cylinder 251 return to the initial state. Then, thebottom plate 203 of the deposition source 200 returns to its initialposition, and thereafter, new deposition material is supplied to thedeposition source 200.

On the other hand, FIG. 4 shows that the optical sensor 253 acting asthe sensing means is installed at the lower surface of the baffle 204,but the optical sensor can be installed at any positions including thelower surface of the top plate 201 as long as the optical sensor 253does not hinder the deposition process and can sense the distancebetween the surface of the deposition material 20 and the top plate 201.

In the deposition sources 100 and 200 according to the first and secondembodiments as described above, when the thickness of the depositionmaterial 20 caused by consumption thereof during the deposition processis changed, the distance between the surface of the deposition material20 and the top plate 101 (the first embodiment) or the distance betweenthe surface of the deposition material 20 and the substrate 12 (thesecond embodiment) can be maintained at the initially-set distance bythe movement of the top plate 101 (the first embodiment) or the bottomplate 203 (the second embodiment). Thus, an appropriate amount of heatis transferred to the deposition material 20 during the depositionprocess so that the deposition temperature of the deposition material 20can be maintained uniformly and the optimum deposition rate can bemaintained.

In the second embodiment, especially, the distance between the top plate201 and the deposition material 20 as well as the optimum distancebetween the substrate and the deposition material are always maintained,and so it is possible to form a uniform deposition layer. Also, thedeposition material adjoining the surface of the bottom plate 203 can bevaporized so that it is possible to minimize the residual of thedeposition material.

In particular, in a case where the deposition material is supplied tothe maximum, all of the deposition material can be vaporized, and thetime loss caused by vacuuming, heating, and cooling processes to beperformed in the deposition chamber after replenishing the depositionmaterial can be minimized. Therefore, the second embodiment enables thedepth of the deposition source to make deeper than the conventionaldepositional source, and so the quantity of the deposition materialsupplied to the deposition source can be maximized.

Third Embodiment

FIG. 5 is a sectional view of the deposition source according to thethird embodiment of the present invention. The deposition source 300according to this embodiment has a vessel consisted of a top plate 301acting as the heating means, a side wall 302, and a bottom wall 303. Thestructure of the top plate 301, on which a vapor efflux aperture 301A isformed and to which a baffle member 304 is fixed, is the same as the topplates 101 and 201 of the deposition sources 100 and 200 of the firstand second embodiments, respectively. Therefore, a further detaileddescription thereon is omitted.

The important aspect of the deposition source 300 shown in FIG. 5 isthat a number of coils C1, C2, . . . Cn as a heating means fortransferring heat to the deposition material 20 are wound around theside wall 302, and a casing 350 is located at the outer side of the sidewall 302.

A number of coils C1, C2, . . . Cn are wound on the outer circumferencesurface of the side wall 302. The uppermost coil C1 coincides with thesurface of the deposition material 20 received in the deposition sourcewith the maximum height (thickness), and the lowermost coil Cn coincideswith the surface of the bottom wall 303.

The coils C1, C2, . . . Cn are arranged for electric power to beindividually applied thereto. A control means (not shown) controls theelectric power applied to each coil C1, C2, . . . Cn, and the controlmeans is connected to a sensing means 353 (for example, optical sensor)which is mounted to the interior of the deposition source.

The function of the coils C1, C2, . . . Cn arranged and described asabove is as follows.

In the early stage of the deposition process, the surface of thedeposition material 20, which is supplied into the deposition source 20with the maximum height, coincides with the uppermost coil C1. At thistime, electric power is applied to only the uppermost coil C1, not theother coils C2, . . . Cn, by the control means. The upper side of thedeposition material 20 is heated and vaporized by the heat generated atthe top plate 301 acting as a heating means and by the heat generated atthe uppermost coil C1.

In the depositing process, the quantity of the deposition material 20received in the deposition source 200 is decreased gradually by theheating and vaporizing action (that is, decrease of the height of thedeposition material 20).

The sensing means 353 mounted on the lower surface of the baffle 304senses change of the height of the deposition material 20, and transmitsthe sensed signal to the control means. Then, the control meanscalculates the height of the deposition material 20 on the basis of thesignals transmitted from the sensing means 353. According to thecalculated height of the deposition material 20, the control meanscontrols the electric power applied to the other coils C1, C2, . . . Cn.

That is, when the height of the deposition material 20 is reduced andthe surface of the deposition material 20 corresponds to the second coilC2 positioned below the uppermost coil C1, the control means blocks theelectric power applied to the uppermost coil C1 and applies the electricpower to the second coil C2.

In succession, if the surface of the deposition material 20 correspondsto the lowermost coil Cn, the control means applies the electric powerto the lowermost coil Cn and blocks the electric power applied to theother coils C1, C2 . . . .

As described above, in the depositing process, even though the height ofthe deposition material 20 is changed, any one coil to which theelectric power is applied always corresponds to a portion of thedeposition material 20 to which the heat generated by the top plate 301is transferred. Therefore, it is possible to prevent the heat generatedby the coils C1, C2, . . . Cn from transferring unnecessarily to theportion of the deposition material which heating and vaporizing do nottake place and the deposition material is not present.

On the other hand, the casing 350 located at the outer side of the sidewall 302 prevents the heat generated at each coil C1, C2, . . . Cn fromradiating outward. Thus, most of the heat generated at each coil C1, C2,. . . Cn is transferred to the deposition material 20 through the sidewall 302 so that it is possible to minimize heat loss. Particularly, ifthe space formed between the side wall 302 and the outer casing 350 isfilled with a thermal insulation material, the heat radiation isprevented more effectively to minimize thermal gradient in the entiresystem. The reference numeral 350A indicates the opening formed on thecasing 350 for connecting power lines to the coils C1, C2, . . . Cn.

More excellent adiabatic property can be obtained by forming the casing350 with oxide or nitride of aluminum (Al), zirconium (Zr), silicon(Si), yttrium (Y), etc., having high thermal capacity.

Another feature of the deposition source according to this embodiment isshown in FIG. 6. FIG. 6 is a sectional view taken along the line 6-6 inFIG. 5 and shows a recess 303A formed at the lower surface of the bottomwall 303 and a coil C received in the recess 303A.

The recess 303A is formed to the longitudinal (or widthwise) directionon the bottom wall 303, and consists of many linear portions andconnection portions connecting two neighboring linear portions. Thus,the single coil C is spread on the entire surface of the bottom wall303. Both ends of the coil C are connected to the power supply (notshown).

When the deposition process is performed, the electric power is appliedto any one of the coils C1, C2, . . . Cn wound around the side wall 302as well as the coil C received in the recess 303A of the bottom wall 303(surely, the electric power is applied to the top plate 301 acting as aheating means). Therefore, the heat generated at the coil C received inthe recess 303A of the bottom wall 303 is transferred to the depositionmaterial adjoining the surface of the bottom wall 303.

In the deposition source according to third embodiment as describedabove, in the processing the depositing process, even though a height ofthe deposition material is changed, the coil to which the electric poweris applied is always corresponded to a portion of the depositionmaterial to which heat generated by the top plate is transferred.Therefore, it is possible to prevent heat generated by the coils fromtransferring unnecessarily to a portion of the deposition material whichis not heated and vaporized and a portion of the deposition source inwhich the deposition material is not present.

Also, the casing provided at the exterior of the side wall prevents theheat generated at the coils mounted to the side wall from radiatingoutward, and so most generated heat is transferred to the depositionmaterial through the side wall to minimize thermal gradient in theentire system.

In addition, when an additional coil is provided at the bottom wall ofthe deposition source, sufficient heat can be transferred to thedeposition material which is remotely located from the heating means(that is, the deposition material adjoining the surface of the bottomwall), and so all of the deposition material can be used effectively anda uniform deposition layer can be obtained.

Fourth Embodiment

FIG. 7 is a schematic perspective view showing relationship between thedeposition source according to the fourth embodiment and the substrate.An inner structure of the deposition source 400 is not shown in FIG. 7.

The deposition source 400 according to this embodiment is consisted of atop plate 401 with certain length and width, a side wall 402, and abottom wall. A vapor efflux aperture 401A is formed on the top plate401. An organic electroluminescent vapor deposition material is receivedin the space formed by the top plate 401, the side wall 402, and thebottom wall.

A feature of this embodiment is to constitute the deposition source 400whose effective deposition length (that is, length A of the vapor effluxaperture 401A of the top plate 401 actually contributing to thedeposition process) is longer than, or the same as, the width b of thesubstrate 12 on which the electroluminescent layer is formed.

FIG. 8 a is a plane view of the substrate showing the initial state thatthe electroluminescent layer is formed on the surface of the substrateby means of the deposition source 400 shown in FIG. 7. If the depositionsource 400 as described above is used for forming the electroluminescentlayer on the surface of the substrate 12, the deposition material'svapor is diffused through the aperture 400A of the top plate 401, andthen dispersed and deposited uniformly on the surface of the substrate12 over the entire width.

The more effective deposition process can be performed by moving thedeposition source 400 constructed as described above or the substrate 20to the longitudinal direction of the substrate. That is, when thedeposition source 400 or the substrate 20 is moved horizontally(linearly) to the arrow direction shown in FIG. 8, theelectroluminescent layer as shown in FIG. 8 a is continuously depositedon the surface of the substrate 12 over the entire length. Ultimately,as shown in FIG. 8 b showing the surface of the substrate on which thedeposition of the electroluminescent layer is completed after movinghorizontally the deposition source 400 or the substrate 12, the uniformelectroluminescent layer is formed on the entire surface of thesubstrate 12.

On the other hand, each respective deposition source 100, 200, 300 and400 described in the first to fourth embodiments has the inner spacedivided into the lower and upper portion, and the cross sectionalsurface of the lower portion is the same as that of the upper portion.Therefore, the flow rate of vapor of the deposition material at thelower portion is practically equal to the flow rate at the upperportion. Also, due to the large surface area of the upper portion of thedeposition source, heat loss of the deposition material in the innerspace is increased. In order to eliminate the above drawbacks, thepresent invention modified the shape of the deposition source.

FIG. 9 a to FIG. 9 d are sectional views of the deposition sources, andshow various shapes of the deposition source according to the presentinvention. Another feature of the deposition sources 500A, 500B, 500C,and 500D according to the present invention is that the sectionalsurface area of the upper portion at which the aperture is formed issmaller than that of the lower portion.

Though the sectional surface areas in a tube can be different indifferent positions, the quantity of flow is same anywhere in the tube,and therefore, the flow rate of a portion having smaller sectionalsurface area is higher than that of another portion having largersectional surface area.

Consequently, just before diffusing vapor of the deposition materialthrough the aperture, the flow rate of vapor at the upper portion havingsmaller sectional surface area is higher than that of vapor at the lowerportion of the deposition source. Higher flow rate induces increase ofthe vapor's kinetic energy (molecules of the vaporized depositionmaterial), and so the density and uniformity of the deposition layerformed on the substrate can be enhanced. Also, since the sectionalsurface area of the upper portion through which the vapor of thedeposition material is diffused is small, heat loss outward can beminimized and the deposition source is not influenced by such exteriorinterference as change of ambient temperature.

In the present invention, on the other hand, a material having higherthermal capacity than quartz, for example, oxide or nitride of aluminum(Al), zirconium (Zr), silicon (Si), or yttrium (Y), or compositematerial of at least two above, is used as the deposition source'smaterial. The thermal capacity of these metal oxide or nitride is largerthan organic material used as the deposition material (about 3:1), andtherefore, the adiabatic property of the deposition source can beimproved.

The preferred embodiments of the present invention have been describedfor illustrative purposes, and those skilled in the art will appreciatethat various modifications, additions, and substitutions are possible,without departing from the scope and spirit of the present invention asdisclosed in the accompanying claims.

1. A deposition source for forming deposition evaporation organicelectroluminescent layers onto a substrate, by applying a vaporizeddeposition material generated therein onto the substrate, and bytransferring heat to a vapor deposition material received therein ontothe substrate, and by transferring heat to a vapor deposition materialreceived therein, said deposition source comprising: a top plate thatsupplies heat to said deposition material and which has a vapor effluxaperture thereon; a baffle member fixed to the top plate by supportingmembers under the top plate; a sensing device disposed on said bafflemember, sensing a height of said deposition material and generatingsensing signals corresponding to the height of said deposition materialwherein a backing surface of said sensing device faces said bafflemember and a front surface of said sensing device faces the liquidsurface of said vapor deposition material inside the container; a bottomplate; a side wall disposed between the top plate and the bottom plate;a plurality of heating coils disposed on an outer surface of the sidewall from a first position corresponding to said sensing device in saiddeposition source to a second position corresponding to an inner bottomsurface of the bottom plate, wherein the plurality of heating coils areelectrically separated each other; a controller that selectively applieselectric power to only a heating coil disposed on a positioncorresponding to the height of said deposition material according to thesensed signals.
 2. The deposition source according to claim 1, whereinthe bottom plate comprises a groove on an outer surface of the bottomwall, and at least one heating coil is received in the groove.
 3. Thedeposition source according to claim 1, further comprising a casingdisposed outside of the side wall that prevents the heat generated bythe heating coils from being transferred to an exterior.
 4. Thedeposition source according to claim 3, wherein a space between the sidewall and the casing is filled with a thermal insulating material.
 5. Thedeposition source according to claim 3, wherein the casing is made of anoxide or nitride of an element selected from the group of consisting ofzirconium (Zr), silicon (Si), and yttrium (Y).